The invention relates to a posterior chamber implant lens of a homogeneous, clear synthetic material, acting as a replacement for the natural lens surgically removed, in particular extracapsularly, from the eye of a living being of a higher order, which
(a) has a central lens body and
(b) has holding means on the lens body extending radially outwards from its periphery and fixing it in its position, being of a homogeneous, clear, vulcanized silicone rubber.
Some time past (1949), Ridley in England, attempted to replace extracapsularly removed eye lenses with artificial acrylic glass lenses implanted in the posterior chamber of the eye. However, these attempts more or less failed due to various reasons, inparticularly due to reasons of insufficiently formed lenses and poor material, as well as due to insufficient sterilization, and for this reason a change was made to implant lenses of polymethyl methacrylate (PMMA) which consist of a planoconvex disk on which holding means or support elements of various types are attached, in the anterior chamber of the eye of living beings, in particular human beings, in front of the iris. However, this method also did not bring striking success, and for this reason, in recent years, the lenses of the type in question were attached to the iris with wire or plastic side pieces and possibly sewn onto the iris.
Apart from PMMA, polyamides were also used as material for such lenses. The disadvantage of these materials lies in particular in the fact that the lenses made out of them cannot be surgically perfectly sterilized. None of the hitherto conventionally used implant lenses can stand up to the heat sterilization by means of overheated steam or hot air, which must be used in order to reach a correct, germ-free sterilization (including bacteria spores).
Accordingly, surgery was forced to make do with subjecting the implant lenses to a chemical liquid degermination, i.e. virtually disinfecting them immediately after production, and then preserving them in more or less suitable liquids in ampoulated form. The lenses are removed from these ampoules immediately before the operation. The limitations of such a chemical liquid degermination lie in the present case in their not being able to destroy bacteria spores, furthermore, these--not indifferent--chemicals easily accumulate in plastic bodies within the eye in an uncontrolled manner and over a longer length of time, due to an exponential function. This material behavior gives cause for concern, particularly for an eye implant.
Through the DE-AS No. 26 07 462 an implant lens became known based on the same inventor. This lens is to be attached to the iris and is to be made of a very particular silicone rubber. The suggestion of selecting this plastic material had the important advantage that the lenses could, for the first time, be sterilized using steam or hot air with the sufficiently high temperatures.
Implant lenses of the first generation, after Ridley placed his acrylic glass lens in the posterior chamber of the eye or in the lens capsule, were lenses of this aforementioned type. As a result of the then soon occurring, considerable complications, there was a change to implanting anterior chamber lenses which were formed with the most various of structures. However, also these lenses which were described as those of the second generation, did not bring about a solution to the prevailing problems.
Lenses of the third generation was the name given to those lenses which were attached to the iris by means of their holding means arranged on them. The technology for implanting such lenses has been refined and improved. However they are still burdened with the disadvantage that they are made of PMMA or other materials which, seen in a physiological aspect, still encounter a certain amount of risk.
A further disadvantage of these lenses, as also is the case with the anterior chamber lenses, is that, seen from the optical system of the eye, the lens is not lying in a favorable position. The posterior chamber lenses, thus recommended for this reason have however not been able to prove themselves convincingly, on the one hand due to their form and on the other hand due to the material of which they are made.